With developments of technologies, smartphones are used more and more widely and have more and more functions, and smartphones have become requisite electronic apparatuses in people's daily lives. At present, large-screen smartphones have a larger display area to meet a user's requirements for browsing web pages, reading books, watching videos, playing games and so on. Hence, the bezel of the smartphone is getting narrower to increase a screen-to-body ratio so as to improve the user experience. However, the narrower the bezels of the smartphones are, the greater of the difficulties of assembling a display screen and a cover plate in the smartphones.